package com.google.zxing.client.android.camera.helper;

import android.hardware.Camera;
import android.os.AsyncTask;

import java.util.ArrayList;
import java.util.Collection;
import java.util.concurrent.RejectedExecutionException;

import com.google.zxing.client.android.helper.CodeManager;

@SuppressWarnings("deprecation") // camera APIs
public final class AutoFocusManager implements Camera.AutoFocusCallback {
	
	private static final String TAG = AutoFocusManager.class.getSimpleName();
	
	private static final long AUTO_FOCUS_INTERVAL_MS = 2000L;
	
	private static final Collection<String> FOCUS_MODES_CALLING_AF;
	static {
		FOCUS_MODES_CALLING_AF = new ArrayList<>(2);
		FOCUS_MODES_CALLING_AF.add(Camera.Parameters.FOCUS_MODE_AUTO);
		FOCUS_MODES_CALLING_AF.add(Camera.Parameters.FOCUS_MODE_MACRO);
	}
	
	private boolean stopped;
	
	private boolean focusing;
	
	private final boolean useAutoFocus;
	
	private final Camera camera;
	
	private AsyncTask<?, ?, ?> outstandingTask;
	
	public AutoFocusManager(Camera camera) {
		this.camera = camera;
		String currentFocusMode = camera.getParameters().getFocusMode();
		useAutoFocus = CameraConfigurationManager.AUTO_FOCUS && FOCUS_MODES_CALLING_AF.contains(currentFocusMode);
		CodeManager.v(TAG, "Current focus mode '" + currentFocusMode + "'; use auto focus? " + useAutoFocus);
		start();
	}
	
	@Override
	public synchronized void onAutoFocus(boolean success, Camera theCamera) {
		focusing = false;
		autoFocusAgainLater();
	}
	
	private synchronized void autoFocusAgainLater() {
		if (!stopped && outstandingTask == null) {
			AutoFocusTask newTask = new AutoFocusTask();
			try {
				newTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
				outstandingTask = newTask;
			} catch (RejectedExecutionException ree) {
				CodeManager.v(TAG, "Could not request auto focus");
			}
		}
	}
	
	public synchronized void start() {
		if (useAutoFocus) {
			outstandingTask = null;
			if (!stopped && !focusing) {
				try {
					camera.autoFocus(this);
					focusing = true;
				} catch (RuntimeException re) {
					// Have heard RuntimeException reported in Android 4.0.x+; continue?
					CodeManager.v(TAG, "Unexpected exception while focusing");
					// Try again later to keep cycle going
					autoFocusAgainLater();
				}
			}
		}
	}
	
	private synchronized void cancelOutstandingTask() {
		if (outstandingTask != null) {
			if (outstandingTask.getStatus() != AsyncTask.Status.FINISHED) {
				outstandingTask.cancel(true);
			}
			outstandingTask = null;
		}
	}
	
	public synchronized void stop() {
		stopped = true;
		if (useAutoFocus) {
			cancelOutstandingTask();
			// Doesn't hurt to call this even if not focusing
			try {
				camera.cancelAutoFocus();
			} catch (RuntimeException re) {
				// Have heard RuntimeException reported in Android 4.0.x+; continue?
				CodeManager.v(TAG, "Unexpected exception while cancelling focusing");
			}
		}
	}
	
	private final class AutoFocusTask extends AsyncTask<Object, Object, Object> {
		@Override
		protected Object doInBackground(Object... voids) {
			try {
				Thread.sleep(AUTO_FOCUS_INTERVAL_MS);
			} catch (InterruptedException e) {
				// continue
			}
			start();
			return null;
		}
	}
	
}
